How to create sale returns?

i am new in programming .. i am coding a program for Clothing shop .. first i have tables in my db from them sales order , sales returns , ledger account . so i will ask my question after this example . if i made a sales order with 3 items each item with 100 l.e. so the total order will be 300 l.e. ,the system will save this order in the sales order and the 300 with the day date in the ledger account . the next day the client come and want to return an item with 100 . so the system will save this invoice in the sales return table and in the account ledger with 100. till here all of this is o.k. . my problem is in if i opened the same sales order i will find the 3 items again .. i thought that if i opened the sales order again i will find 2 items only , without the returned item . so how can i fix it or there is another way for the sales returns .. ?